The novel opens on William Thornhill's first night in the penal colony of New South Wales in 1806. William sits outside the mud hut assigned to him and his family - his wife Sal and two small children, Willie and Dickie. The hut has a flimsy door made out of bark that offers little protection from the elements or from human trespassers. While his wife and children lay sleeping inside the hut, William stares out into the darkness, feeling the vast forest surrounding him. He cannot sleep, plagued with worry about the life ahead of them.
On the nine-month voyage to New South Wales, William clings to his former life, reliving the familiar bends in the Thames that he rowed each day. As he listens to the foreign sounds of the forest, William realizes that the world he left behind in London is gone forever. Sitting in jail in London with a death sentence hanging over his head, all William could think about was escaping the noose. But now, trapped on the edge of a merciless continent by ten thousand miles of water, he wonders if perhaps death was preferable to this prison without walls. He feels acutely the pain of exile, of being severed from everything he ever knew and loved.
Suddenly, the darkness shifts, and a man appears in front of him. The man's skin is as black as the night, covered with ornamental scars, and he holds a spear. Afraid for his family asleep in the hut, William yells at the man to go away. After the first rush of fear, William finds himself filled with anger at the man's refusal to leave. He raises his arm as if to hit the man and yells at him again to go away.
The man stands firm, unaffected by William's anger. Then, the man begins to speak, and William hears his own phrase repeated back to him - Be off! The man waves angrily at the ocean and says again, Be off! Stunned, William says nothing, but he does not give way. For better or for worse, he is alive. All he has left is the mud hut and his family sleeping inside. William decides that he will not surrender his last chance at life to a naked man, even one with a spear. After a tense silence, the man disappears into the night, and William is left with the memory of that jagged spear and a sense of vulnerability in the face of an entire continent filled with men armed with spears.
In the title of the prologue to The Secret River, Grenville introduces one of the main themes of the novel - the clash of civilizations between the Aborigines and the colonists. Each people finds the other 'strange' in practically every aspect of life, from the color of their skin to the structure of their society. The novel chronicles the moral dilemmas and conflicts that arise from the meeting of these two 'strangers.'
William's first encounter with an Aborigine sets out the issue at the heart of this historic meeting - the claim to the land. The Aborigines consider the land their birthright and resent, and eventually resist, the invasion of an alien people. The settlers, however, are caught in a bind. As convicts deported to New South Wales from England, they cannot leave. The land itself is their prison. The colonists can either succumb to drink or carve out a place for themselves on the forbidding continent.
William refuses to back down to the Aborigine's demand that he leave because he can not give up the only things he has left - his family and the chance to create a future for them. Both the Aborigine and William demand that the other 'be off.' In order for the Aborigines to preserve their culture, the white man must leave. In order for William and the other colonists to build a life in Australia, the Aborigines must be 'tamed' and dispersed. Grenville discusses this theme throughout the novel, exploring the possibility of the two cultures living side by side and telling the story of that possibility's demise.
In the encounter between William and the Aborigine, Grenville also examines the feeling of power that comes into play in the interaction between the Aborigines and the colonists. The racial prejudice that the colonists bring with them to Australia sets the stage for the callous and often violent treatment of the Aborigines in the novel. Denied their freedom and placed in a humiliating and degrading position, the convict settlers enjoy the feeling of no longer being on the bottom rung of society. Even they can claim superiority over the 'blacks.' William experiences his first feeling of strength and manliness since his arrest when he stands up to the "naked black man."
Grenville also uses the prologue to introduce the theme of exile. William longs for the sights and smell of the Thames as he lays on his bunk in the cramped ship. The misery that he feels as he sits in front of the mud hut in the settlement, unnerved by the foreign smells and sounds, represents the sense of displacement experienced by the exiled. Grenville explores this theme throughout the novel in the character of Sal, whose memories and imagination remain firmly rooted in the land of her birth.